Silencer



May 11 1926.

' H. P. MAXIM SILENCER Filed Jan. 2, 19 23 INVENTOR ATTORNEYS Patented May 11, 1926.

UNITED STATES I l,584,315 PATENT OFFICE.

HIRAM PERCY MAXIM, OF HARTFORD, CONNECTICUT.

SILENCER.

Application filed January 2, 1923. Serial No. 610,200.

The present invention relates to silencers or mufflers such as are used in connection with gas engines to dead'en the noise of the exhaust.

Certain objects of the invention are to provide a silencer of improved and simplified construction, having a minimum number of component parts, to materially reduce the cost of manufacturing the parts of the silencer and thereby to provide a type of' silencer that is particularly adapted for economical quantity production; to provide an effective exhaust silencer inwhich a minimum amount of back pressure will be developed in use; and to provide a silencer of rugged cast iron construction throughout, in which a series of silencing chambers or passages ai'e compactly arranged to reduce as far as possible the size of the silencer.

A further object is to provide such a silencer of economical construction which embodies features for the rapid dissipation of the energy of the sound waves passing therethrough, and also affording a minimum of back pressure for the accompanying gases which must be exhausted through the silencer.

With these and further objects in View, the invention consists in the features of construction and in the combinations and arrangements of parts hereinafter described and claimed, the advantages of which will be apparent to those skilled in the art.

In the accompanying drawings,

Fig. 1 is a longitudinal sectional view of the improved silencer in what is now considered its preferred form; and

Fig. 2 is a sectional view taken on the line 22 of Fig. l.

Referring to the drawings, the improved silencer therein shown comprises two metallic castings in the form of cup-like shells; 5 and 6 having flanged rims 7 and 8 respectively. -The shells 5 and 6 are coaxially arranged with their flanged rims 7 and 8 abutting end-to-end and secured together by bolts 9 to form an inclosed silencing chamber 10. .The abutting portions of the rims 7 and 8 may be grooved to receive the opposite sides of a packing ring 11 which spend to the ribs 16',

shell 5. The apertures 14 and 15 are similar and either may be utilized as an outlet for the chamber 10 as ma be best adapted to the conditions of use of a particular silencer.

The interior of the shell 5 is provided with a series of concentric annular ribs 16 which arecoaxial with the rimsofthe shell and are cast integrally therewith. The shell 6 is similarly provided with a series of inter- .nal annular concentric ribs 18 which corre I the ribs 18 being cast integrally with the shell 6 and being coaxial with the rim of the shell. The ribs 18 of the shell 6 are of slightly greater diameter than the corresponding ribs 16 of the shell 5 and the ribs 16 and 18 are arranged in overlapping relation to divide the silencer chamber 10 into a series of concentric annular whirl or expanding chambers 20. The adjacent overlapping portions of the ribs 16 and 18 are spaced apart to provide between them relatively narrow passageways 22 connecting adjacent larger expansion chambers 20. It will be noted that the passageways 22 which connect the expansion chambers 20 are very much narrower than said expansion chambers, which substantially narpassageways serve to trap or prevent considerably shorter in length, less than one half, than the expanding or whirl chambers 20, so to facilitate the passage of the gases therethrough with little back pressure.

Such narrow short passageways 22 connecting relatively large passageways 20 act somewhat similarly to a venturi passageway in avoiding check to the free flow of the gases.

The exhaust gases which enter the outermost whirl chamber through the tan ential inlet 12, are whirled around within the chamber until they pass through the outermost annular narrow passageway 22, into the middle whirl chamber. whirl chamber the gases pass, through the respective annular narrow passageway 22, into the innermost whirl chamber and thence through .the innermost passageway 22 into the center of the silencer from which they escape through one or the other of the apertures 14 and 15. During theassa e of the gasesthrough the concentric W irlc ambers, the sound waves are permitted to expand into each successive chamber 20 and a large part of the energy of each sound From the middle wave is trapped and only a relatively small number thereof are permitted to escape through the annular outlet passages 22 connected with the chambers 20. This process is repeated in each expanding chamber and when a sound wave finally emerges from the silencer most of its energyhas been dis sipated and the exhaust is practically noiseless. Inasmuch as the gases are introduced tangentially into the silencing chambers, the gases are caused to *whirl rap1dly therethrough and very little back pressure 1s created.

The rapid dissipation of the sound energy and consequent silencing of the sound effect within the silencer above described will be readily appreciated by considering the passage of a single sound wave. therethrough. A sound wave entering the inlet at 12 spreads out into the outermost annular chamber 20, and as it travels from right to left, (vlewmg Fig. 1) it expands slightly when passing the end of the rib 18, due to the slight enlargement of said passageway 20. This sl1ght expansion of the sound wave reduces its energy per unit of area, and upon 1ts reflection from the wall at the end of the chamber 20 only a small fraction of this sound wave is permitted to pass through the verymuch narrower passageway 22, the rest of the wave being trapped in the chamber 20. The small fraction of said sound wave travell ng through the passageway 22, upon reach ng the next innermost enlarged expanding chamber 20, again expands with consequent diminution of energy per unit of area in said sound wave. A fraction only of this expanded wave then passes through the next narrow passageway22.

The above process is thus continued throughout the remaining chambers and narrow passageways to the innermost central exit opening 15, so that eventually very little energy per unit of area in the sound wave is permitted to reachthe outside of the silencer. The arrangement of expanding chambers 20 alternating with the comparatively narrow passageways 22 connecting thelarger chambers contributes largely to k the reduction of the sound wave energy which is finally emitted from the silencer and is an important feature of the present invention.

"The above described silencer comprises only two parts, namely, the shells 5 and 6 and these shells are so designed that they are particularly easy to cast and as a result there will be a minimum amount of loss in the foundry by reason of injury to the castings while they are being made. The shells, after being'cast require no machine work and they may be readily and quickly assembled; These advantageous features make the hereindescribed "silencer particularly adapted. for economicalq'uantity produ tion.

In the present construction, furthermore, the parts of the silencer casing are rigidly secured together without the necessity of passing tie-rods through the silencing chambers thus insuring uninterrupted passages for the gases. I

The invention having been described, is claimed is 1. In a silencer of the type wherein a series of concentric expansion chambers are interconnected to afford a continuous pasageway for a sound propagating medium, a cylindrical casing, a plurality of spaced annular ribs projecting from the inner face of each end wall of said casing to subdivide the latter to form said chambers, the ribs carried by one end wallhaving their free extremiwhat ties overlapping and spaced from the free I casing, one of said casing parts having a tangential inlet in its side wall and an axial outlet in its end wall and the other of said casing parts having an axial outlet in its end wall, annular flanges projecting from the side walls of said casing parts, adjacent said plane of division, bolts extending through said flanges for securing said casing parts together, and a series of annular ribs formed within and coaxial with each casing port and relatively arranged when the casing parts are assembled to provide a series of concentric expansion chambers the outermost of which is in combination with said inlet and the innermost of which is in communication with said outlet, the ribs of one of said casing parts overlapping the ribs of the other casing part and said overlapping ribs being spaced from each other to provide passageways affording communication between adjacent expansion chambers, which passageways are su stantially narrower than said expansion chambers.

3. In a silencer of the type wherein a series of concentric expansion chambers are interconnected to afford a continuous passageway for a sound propagating medium, a cylindrical casing, a plurality of spaced annular ribs ,projectin from the inner face of each end wall of sai casing to subdivide the latter to form said chambers, the ribs carried by one end wall having their free ex tremities overlapping and spaced from the free extremities of corresponding ribs carried by the other end wall to provide a series of coaxial annular passa eways interconnecting said chambers, witch passageways are substantially narrower than said expansion chambers and less than half the length of said expansion chambers.

4. In a silencer of the type wherein a series of concentric expansion chambers are interconnected to afford a continuous passageway for a sound propagating medium, a cylindrical casing, a plurality of spaced annular ribs projecting from the inner face of each end wall of said casing to subdivide the latter to form said chambers, the ribs carried by one end wallhaving their free extremities overlapping and spaced from the free extremities of corresponding ribs carried by the other end wall to provide a' series of coaxial annular pasageways interconnecting said chambers, which passageways are substantially narrower than said expansion chambers, a tangentially disposed inlet for the outermost chamber and an axially disposed outlet for the innermost expansion chamber of said, series.

5. A silencer comprising two cup-like shells coaxially arranged and secured together -in abutting rim-to-rim relation to. provide an enclosing casing, a plurality of' annular ribs formed within and coaxial with each shell, the ribs of one shell overlapping the corresponding ribs of the other shell to Certificate It is hereby certified that in Letters upon the application of Hiram Percy Maxim, an error appears in the printed specification requiring 2, line 107, claim 2, .for

and'that the said Letters Patent should be read same may conform to the record of the case 'in'the Patent Office. Signed and sealed this 8th day of June, A. D. 1926.

improvement in Silencers, correction as follows: Page communication,- therein that the one shell overlapping of the other shell to dividethe interior of said casing into a se-- ries of concentric expanding chambers, and the overlapping portions of said ribs being spaced apart slightly to provide passageways between adjacent expanding chambers, which passageways are substantially narrower than said expanding chambers, a tangenti ally disposed inlet for the outermost expanding chamber and an axially disposed outlet for the innermost expanding chamber of saidseries.

In testimony whereof I have aflixed my signature.

HIRAM PERCY MAXIM.

of Correction.

Patent No. 1,584,315, granted May '11, 1926,

of Hartford, Connecticut, for an the word combination read with this correction i M. J. MOORE, Acting Gammz'ssioner of Patents. 

